Warring parties in Sudan's Darfur region have been given extra time to reach a deal after missing a deadline.
Rebel groups have misgivings about the AU peace plan
"We have to stop the clock for the next 48 hours to allow the parties to hold more talks," the African Union's chief negotiator, Salim Ahmed Salim, said.
The Sudanese government has agreed to sign the AU-backed agreement, but the rebels have no common position.
Two of the rebel factions have rejected the deal as it stands, but the main SLA group has not ruled out an agreement.
African Union (AU) mediators agreed to an extension after a deadline at talks in the Nigerian capital, Abuja, passed without a deal at midnight on Sunday.
"If we walk away from here, without a peace deal, the world will not forgive us," Mr Salim said at a late-night meeting.
The extension, until midnight on Tuesday, came after a request from US officials for more time for the parties to resolve outstanding issues.
The BBC's Alex Last in Abuja says the mediators continue to shuttle back and forth between the two sides, seeking a breakthrough.
The peace plan in question calls for pro-government Arab militias to be disarmed, and for rebel fighters to be incorporated into Sudan's forces.
The 85-page draft also aims to end what Darfur rebels say is long-standing neglect of the province by the Khartoum government.
It calls for a one-off transfer of $300m to Darfur, with $200m a year for the region thereafter.
The small Justice and Equality Movement (Jem) and one faction of the main group, the Sudan Liberation Army (SLA), refused to sign the deal as the midnight deadline passed.
Jem spokesman Ahmed Hussein told the BBC the peace plan failed to address his group's "minimum demands" and favoured the Khartoum government.
However the chief negotiator of the SLA left the possibility open that a deal could be reached.
Hundreds of thousands have been displaced by the violence
Concern over the demand for rebel forces to lay down their arms before they are integrated into the Sudanese army appeared to be one sticking point.
Mr Salim said the rebels are refusing to budge on a demand for one of Sudan's vice-presidents to come from Darfur.
But Khartoum says it has conceded enough.
"There is no room for any other concessions because any other agreement will be to the detriment of the whole Sudanese region," Sudanese Justice Minister Muhammad Ali al-Maradi told the BBC.
"They will have to be reasonable and they have to pay also a price for this peace."
As the talks continued, campaigners held a series of mass rallies across the United States calling for an end to the conflict.
Speakers in Washington included the actor George Clooney, who described Darfur as "the first genocide of the 21st Century".
But Mr al-Maradi dismissed such claims, telling the BBC this was "sheer propaganda".
The AU - which has 7,000 peacekeepers in Darfur - has struggled to stop the violence between the rebels and the government-backed Janjaweed militias.
Over the past three years, the Darfur conflict - which began when rebel groups began attacking government targets - has become a regional crisis drawing in Chad, Eritrea and the Central African Republic.
The conflict has killed 200,000 people and driven more than two million from their homes.
The BBC's Africa Analyst Martin Plaut says the talks in Abuja are a last effort attempt to maintain the fading credibility of the AU, while preventing the flames of war from spreading beyond the borders of Sudan.